It does have an Alternate Leaf Pattern like poison ivy does. My initial guess would be, no this is not poison ivy. There are not any types of poison ivy that have thorns. There are types with "hair", if you would describe this as a softer 'grippy' type of texture rather than true thorns (which is what this looks like). Though I cannot appropriately identify it, I would definitely be leery of the it.

I am not an early bird or a night owl--I am some form of permanently exhausted pigeon

It is a type of Rubus. It could be a wild form of Raspberry but it is difficult to identify from the photos. You can let it grow and see what type of fruit it yields next year, then decide if you want to yank it or keep it.